1. Field of the Invention
The invention is directed to a cardiac valve prosthesis.
2. Description of Related Art
The natural cardiac valves are tricuspid or bicuspid valves which have two or three flaps, respectively, and, technically speaking, fulfill the function of nonreturn valves allowing the blood to pass in one direction but stopping it in reverse direction. If the natural cardiac valves are to be replaced by mechanical pendulum-disk type or tilting-disk type prostheses, there are inserted monocuspid or bicuspid valves wherein closing bodies, by the blood pressure or the blood flow, are movable within a valve ring which is sutured to the respective opening of the heart. Long-term use of such cardiac valve prostheses can result in massive problems, necessitating life-long administration of anticoagulants to the patient or replacement of the prosthesis. For example, there is the danger of thrombi occuring at the valve ring or at the fastening means for the closing body, which thrombi impair the easy action of the closing body and the fluid-tightness of the cardiac valve prosthesis. Further, body tissue can grow into the flow path of the blood. The danger of thrombi being formed is imminent particularly at the journal pins of the closing body which engage into the recesses of the valve ring. Therefore, particular precautions must be taken to safeguard the flowing movement of the blood around the journal pins and through the recesses receiving the journal pins.
U.S. Pat. No. 4,799,930 describes a cardiac valve prosthesis in which the journal pins of the valve ring are supported in articular sockets having at least one flushing channel leading therethrough. On the one hand, such an articular-socket structure is difficult to manufacture, and on the other hand, it does not provide the required mobility of the closing body.
In a cardiac valve prosthesis as known from European publication No. 0 113 681 Al, the wall of the valve ring is provided with recesses being larger in diameter than the journal pins of the closing body so that the journal pins, during the opening and closing movement of the closing body, perform a translatory movement. Said recesses are troughs or blind holes, with the front ends of the journal pins sweeping over the bottom of the recesses in the manner of a windshield-wiper when the valve ring is moved. Thereby, a wiping effect is obtained with each movement of the closing body. However, it is disadvantageous that not all of the surface portions are subjected to said wiping effect equally and that in the recesses, especially at their edges, there are generated areas of possible thrombi formation.
In known cardiac valve prostheses, recirculation flows and dead-water areas occur in the journaling areas of the closing bodies, resulting in insufficient wash-out of the contact areas between valve ring and closing body. Thrombi adhering to these areas provoke the danger of incomplete opening and closing movements.
It is an object of the invention to provide a cardiac valve prosthesis in which the generation of thrombi in the supporting areas, being especially susceptible to thrombi, is prevented.